The present invention is concerned with a mould tool assembly. More specifically, the present invention is concerned with a fluid heated and cooled mould tool assembly in which the back face of the mould tool is heated and cooled by impingement of a fluid jet.
By influencing the temperature of a mould face during the moulding of plastics, composites and the like, the curing process can be controlled, and the properties of the workpiece tailored to specification. The temperature of such moulds can be controlled by the use of a fluid jet impinging on the back face of either or both opposing tools, A first side of the tool defines mould face against which a workpiece is moulded, and a second, opposite, side defines a temperature control face (in thermal contact With the mould face). Fluid jets are directed onto the temperature control face in order to selectively heat and cool the tool. The fluid jet can be heated by an in-line air heater, or simply directed at ambient temperature in order to provide a cooling effect. This selective heating and cooling can influence the properties of the material within the mould to produce the desired results. The moulding of parts with variable thickness, properties and or geometry can be controlled by subdividing the tool into a plurality of zones, each of which is individually controlled.
A problem with using such impinging fluid jets is that in high speed, high power heating and cooling, the temperature gradient across an individual zone can vary considerably, For example, if a high power fluid jet (for example, 250 kilowatts per metre squared) impinges on the centre of a temperature control face, then a significant temperature gradient can arise from the impingement point to the edges of the zone. Similarly, attempts to rapidly cool the tool can result in high temperature gradients. This is undesirable. It is desirable to equalise the temperature across the zone.
One solution to this problem is to coat the underside of the mould (i.e., the temperature control surface) with a high conductivity material such as copper.
Although this provides additional conductivity between the impingement region and the edge of the tool, significant temperature gradients still exist.
It is an object of the present invention to overcome or at least mitigate the above referenced problem.